Optical film and method for production thereof

Abstract

The invention relates to an optical film containing polymers having different repeating units, and methods for production thereof. Further, the invention also relates to an optical laminate, a polarizing plate, and an image display device each using the optical film. The optical film of the invention advantageously has not only high solubility in solvents but also a high level of transparency since the polymers used in the optical film are compatible with each other. Further, wavelength dispersion of the birefringence of the optical film can be controlled by merely changing a ratio of polymers.

The invention claimed is: 
     
       1. An optical film comprising:
 a polymer having a repeating unit represented by Formula (III); and 
 a polymer having a repeating unit represented by Formula (II); 
 
       
         
           
           
               
               
           
         
         wherein in Formula (III), A 1  and B 1  each represents a substituent on the benzene ring, and a 1  and b 1  each represents the number (an integer of 0 to 4) of the corresponding substituents represented by each of A 1  and B 1 , A 1  and B 1  each independently represents hydrogen, halogen, an alkyl group of 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group, R 1  and R 2  each independently represent a straight-chain or branched alkyl group of 1 to 10 carbon atoms or a substituted or unsubstituted aryl group, R 3  to R 6  each independently represent a hydrogen atom, a halogen atom, a straight-chain or branched alkyl group of 1 to 6 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, or a substituted or unsubstituted aryl group, provided that at least one of R 3  to R 6  is not a hydrogen atom; 
       
       
         
           
           
               
               
           
         
         wherein in Formula (II), A 2 , D 2 , and E 2  each represent a substituent on the benzene ring, and a 2 , d 2 , and e 2  each represent the number (an integer of 0 to 4) of the corresponding substituents represented by each of A 2 , D 2 , and E 2 , A 2 , D 2 , and E 2  each independently represent hydrogen, halogen, an alkyl group of 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group, X 2  represents a single covalent bond, an unsaturated double bond, an unsaturated triple bond, or at least one atom or group selected from the group consisting of a CH 2  group, a CHR group, a CR 2  group, a C(CZ 3 ) 2  group, a CO group, an O atom, a S atom, an SO 2  group, an Si(CH 2 CH 3 ) 2  group, and an N(CH 3 ) group, wherein R each independently represent a straight-chain or branched alkyl group of 1 to 6 carbon atoms or a substituted or unsubstituted aryl group, Z represents halogen, r 2  represents 1 or 2, and p 2  and q 2  each represent an integer of 1 to 3. 
       
     
     
       2. The optical film according to  claim 1 , wherein Formula (II) is Formula (IV) below; 
       
         
           
           
               
               
           
         
         wherein in Formula (IV), A 2  and a 2  each have the same meaning as in Formula (II), R 7  and R 8  each independently represent a straight-chain or branched alkyl group of 1 to 6 carbon atoms or a substituted or unsubstituted aryl group, R 9  to R 12  each independently represent a hydrogen atom, a halogen atom, a straight-chain or branched alkyl group of 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group (provided that at least one of R 9  to R 12  is not a hydrogen atom. 
       
     
     
       3. The optical film according to  claim 2 , wherein R 7  in Formula (IV) is a methyl group, and R 8  in Formula (IV) is a straight-chain or branched alkyl group of 2 to 4 carbon atoms. 
     
     
       4. The optical film according to  claim 2 , wherein R 9  to R 12  in Formula (IV) are each independently a straight-chain or branched alkyl group of 1 to 4 carbon atoms. 
     
     
       5. The optical film according to  claim 2 , wherein R 1  in Formula (III) is a methyl group, and R 2  in Formula (III) is a straight-chain or branched alkyl group of 2 to 4 carbon atoms. 
     
     
       6. The optical film according to  claim 2 , wherein R 3  to R 6  in Formula (III) are each independently a straight-chain or branched alkyl group of 1 to 4 carbon atoms. 
     
     
       7. The optical film according to  claim 1 , wherein the polymer having the repeating unit represented by Formula (III) and the polymer having the repeating unit represented by Formula (II) are in a weight ratio of 1:99 to 99:1. 
     
     
       8. The optical film according to  claim 1 , wherein the optical film has a thickness of 20 μm or less. 
     
     
       9. The optical film according to  claim 1 , wherein the optical film has a ratio D=Rth(450)/Rth(550) of the retardation (Rth(450)) in the thickness direction at a wavelength of 450 nm to the retardation (Rth(550)) in the thickness direction at a wavelength of 550 nm in the range of 1.02 to 2.00. 
     
     
       10. The optical film according to  claim 1 , wherein the optical film has a haze of 1.0% or less. 
     
     
       11. The optical film of  claim 1 , wherein a refractive index (nz) in the film thickness direction of the optical film is smaller than the maximum (nx) an in-plane refractive index thereof. 
     
     
       12. A polarizing plate, comprising a polarizer and the optical film of  claim 1 . 
     
     
       13. An image display device, comprising the polarizing plate of  claim 12 . 
     
     
       14. An image display device, comprising the optical film of  claim 1 . 
     
     
       15. A method for producing the optical film of  claim 1 , comprising the steps of:
 preparing a solution comprising the polymer represented by Formula (III), the polymer represented by Formula (II), and a solvent; 
 applying the solution to a surface of a polymer substrate; and 
 drying the applied solution.